The development of sensor systems for environmental monitoring is a matter of increasing importance in this country. Environmental contaminants are often present in liquids found in the environment as a consequence of a particular manufacturing process and subsequent discharge of the effluent from the process into sewage systems and waterways. Often times, the discharge contains toxic elements such as lead, silver, mercury, various organic compounds and the like. Heretofore, in order to determine whether or not a given contaminant was present, it was necessary to obtain samples in the field and transport them back to a remote laboratory for analysis by techniques such as gas chromatography, mass spectrometry and the like. This is an inefficient means of testing because of the time wasted in traveling from the field to the laboratory, the necessity of preparing samples for analyses, and so forth. It is also very expensive.